Re: [CAD_CAM_EDM_DRO] feeds and speeds.

Hello Ward,
I agree and disagree with you.

"Ward M." wrote:

> I disagree with regards to the tool insert life. Properly cared for inserts
> give much longer life than 20 minutes. Shock loads, both thermal and
> mechanical, are the prime destroyers of carbide tooling. Carbide will
> certainly wear out, but after quite a bit longer than 20 min.

Right: Vibration and hits are notious for carbide.
Wrong: The 20 to 30 minutes are a theoretical value for turning inserts when you use the high values recommended from the factory
for that particular material. As soon you go below that value tool life increases drastically. This is what I was taught in
University, 2 of my suppliers (Sandvik and Kennametal) indicated the same and I proved it in my own shop frequently.
Last and least don't forget the machineability of the same materials from different suppliers vary dramatically. (Test 4140M from
Sweden against 4140 from Brazil)

> Also note
> that there is a MINIMUM chip load to be observed when using carbide. Since
> carbide is so brittle, even ground and honed inserts have a slightly rounded
> edge. The sharpest carbide inserts that I use require a minimum of 0.0015
> chip load and can take up to 0.017 IPR. Non honed or non ground inserts
> have a higher minimum chip load.

OK

>
> 6061 aluminum is not too fun to machine. It is pretty gummy, and coolant,
> either mist or flood, is quite necessary for any useful metal removal rate.
> I much prefer 7075 aluminum for its machining properties as well as its
> superior mechanical properties. The drawback to 7075 is that it has lower
> corrosion resistance, although this is not a problem in most applications.

Here in Costa Rica I get only 3000 series aluminium or 6061 T6511 or 6064 T6511. The accent is on T6511. Which indicates high
machineability.
I cannot refer to others.

> I mill 7075 at up to 75 IPM using mist coolant with Valenite's water
> soluable coolant and a Cool-Mist sprayer. The shop does get sorta foggy
> after a few hours of cutting though. I use flood coolant for all materials
> on the lathe an this works well and doesn't have the fog up problem.

I agree mist on a mill and flood on the lathe work great.

>
> Thanks,
>
> Ward M.
>
> wardmerk@... <mailto:wardmerk@...>

Good Luck
Sven Peter


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